This invention relates generally to medical-electronic apparatus for monitoring the amount of fluid being administered to a patient and for concurrently metering the amount of fluid exhausted therefrom, and more particularly to a computerized body fluid accounting system for use in surgical procedures and in post-operative care which affords a running account of fluid intake and outtake.
In the course of a typical surgical procedure, intravenously (IV) administered to a patient are fluids whose properties are medically appropriate to the procedure. Among these are whole blood or plasma, Ringer's lactate, antibiotics and anti-coagulants as well as saline and dextrose solutions. The multiplicity of such fluid inputs imposes a difficult burden on the attending anesthesiologist or other specialist who, among his other responsibilities, must assess the volume of blood or other fluid which has been infused into the patient.
Since in modern practice, IV solutions are contained in collapsible plastic bags suspended at raised positions on stands, by observing the degree to which a particular bag has collapsed, one may, with a fair degree of accuracy, determine how much of a particular fluid has been delivered to the patient. But when an observer is called upon to monitor four or five hanging IV bags and at the same time to carry out other necessary tasks, his ability to make a reasonably accurate assessment of the fluid inputs may be impaired.
Moreover, it is not enough to assess the volume of fluid inputs to a patient, for proper patient care entails information regarding the prevailing fluid input-to-output balance. The observer must therefore also consider the volume of fluid being excreted or otherwise discharged from the patient through appropriate catheters by way of the urinary, anal or gastrointestinal tract. Also, one must take into account the loss of blood; for in the course of a surgical procedure, blood and other body fluids are extracted from the surgical site by suction pumps as well as by absorbent sponges.
Both the anesthesiologist and surgeons in a surgical procedure must monitor the amount of blood infused to and removed from a patient. Since the surgeon's mind is on one set of immediate tasks and the anesthesiologist's on another (only part of which is monitoring fluid flow), a disparity often arises between the surgeon's and the anesthesiologist's assessments as to how much blood has really been taken out of and put into a patient. In some cases this disagreement is responsible for the loss of the patient due to congestive heart failure, circulatory disfunction, or other volume-related difficulties. With present day high technology surgical methods, it is nearly impossible to keep count of so many variables when they are not centralized at a point where rapid analysis can be made. In a complex operation such as open heart surgery and other cases involving deep thorasic surgery, there may be a multiplicity of suction pumps as well as a multiplicity of surgeons working on a patient. This can occur in emergency conditions or during extremely complex operations; i.e., heart transplants and open heart surgery. In these situations, the automatic tallying of suction fluids is mandated by the fact that it is impossible to keep up with the traffic of fluid loss from a patient when there are several wound sites or surgical routes for fluids to leave the body. A single point integration of data available for reference then becomes imperative.
In the normal course of a surgical procedure with a multiplicity of bags present, it is not impossible for the anesthesiologist to assess precise amounts of fluid, but when there is a crisis in the operating room the full attention of the surgical staff including the anesthesiologist is then directed toward solving the immediate problem. It is during these periods, when fluid balance is at a very critical level and no one has time to pay attention to it, that fluid balance problems tend to arise. In addition, there are instances when surgical fluids such as blood plasma or whole blood in an emergency situation are literally pushed into a patient. That is, the bag connected to the patient through an I.V. line is squeezed very hard to force in as much fluid in as short a time as possible. It then becomes difficult to assess the actual amount of fluid, in that the fluid is being rapidly advanced, and the residuals in the bag do not collect in a gravity environment so that the remainder in the bag can be measured easily by eye.
Under such circumstances, it is easy to see how one may lose track of several units of fluid, for there are more immediate tasks at hand than to write down how much blood was used. When the attention of personnel is concentrated on the most important procedure--i.e., cardiac resuscitation--this activity delays the logging of the fluid input until the crisis has passed. Thus under high stress situations, one may forget to log fluids, and this may not only adversely affect the mitigation of the emergency itself but also the short term survival of the patient as it may relate to the circulatory and vascular system.
The need to be advised as to the body fluid balance (the ratio of total fluid input to total fluid output) is by no means confined to surgical procedures. In post-operative care, whether in a critical care unit or in an intensive care facility, the patient is usually treated intravenously with various medications. Also, means may be provided to continue to draw exudate from the surgical site.
It is essential that the status of medications and their effect on the patient be exactly known, for medicaments not only influence metabolism but also affect post-operative recuperation time and post-operative well being. During the post-operative period, it is vital that careful control be maintained over the input of medicaments; for an excessive amount of certain drugs may have a fatal effect, whereas an insufficiency of others may lead to organ necrosis, cardiac failure, or other terminal disorders.
Even in those procedures where no surgical procedures have been performed on a patient, such as a patient entering a hospital with cardiac arrest, his fluid balance must be very tightly controlled because of the nature of his medical complaint. Under such circumstances, medication may be given to the patient which increases the amount of urine excreted from his body, thus depleting his body of fluid. (The patient probably is under general anesthesia for pain or to induce sleep and cannot advise the medical staff when he needs more fluid to replenish that which his body has cycled.) Therefore, the fluid balance of this patient is critical. With cardiac and pulmonary patients, the body fluid level and the electrolyte balance are critical for basic survival. The concern of this invention is, therefore, not limited to surgical procedures or post-operative care, for it embraces patients who have never had a surgical procedure but have been admitted to the hospital for a variety of other complaints. Among the complaints to which the invention is appropriate are cardiac patients, diabetics, pneumonia patients, patients suffering from pulmonary edema or other pulmonary disfunctions.
Present control procedures for this purpose depend largely on the ability of the attending nurse to carefully check from time to time the various fluid input and output sources and to report any irregularity to the physician in charge. These control procedures are, of course, subject to human error and negligence. The level of work pressure in a crical care unit or cardiac care unit, even in the smaller hospitals, is high. Hospitals are having to treat an increasing number of people on an extreme situation basis, and the facilities of most hospitals have not kept up with the volume. In a case where a critical care unit has ten beds and only three or four nurses to staff those beds, should an emergency occur in one or two of those beds, all attention is diverted to terminating the emergency, the condition of the other patients being ignored for as long as it takes to correct the problem. In some cases, this neglect has been fatal to patients not involved in the emergency.
Not only in terms of work pressure is the problem substantial but also in regard to the complexity and the range of drugs and medication that can be dispensed to a patient. It is easy to miscalculate a dosage for a patient when one has to recalculate the dosage each time the particular drug or medication is administered because of changes in fluid level of the patient. Even with the best of nursing care, there are circumstances when the instantaneous nursing peak work load is too great, and significant or critical parameters of either the patient under immediate concern or other patients in the critical care ward are brushed aside because of lack of staff. Yet the rate at which certain substances are infused and the total amount of the substances given to a patient may make the difference between success or failure.